Vascular prosthesis containing in the wall microcapsules, including hormone-producing cells

ABSTRACT

A vascular prosthesis having a low porosity outer material such as PTFE, and an inner synthetic tubular mesh. Semi-permeable microcapsules that contain hormone-producing cells, are placed between the outer material and the inner mesh. The microcapsules are preferably made of polysaccharides or amino-acid polymers.

This application is a divisional of copending application Ser. No.07/548,372 filed on Jul. 5, 1990, now U.S. Pat. No. 5,104,403. Theentire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to vascular prostheses that containhormone-producing cells in microcapsule form.

2. Description of Related Art

Microcapsules consisting of saccharide, amino-acid polymers and othermaterials, such as agarose polymers, are already known and are apt tocontain living hormone-producing cells.

Microcapsules with the above-mentioned features are manufactured andmarketed by Damon, Biotech of Boston under the name of Encapcell, andalso by other laboratories.

These microcapsules allow for the protection of the cells containedinside the microcapsules against a possible rejection phenomena, whileallowing the metabolic activity of the cells to continue and permit theleaking out of the hormones secreted by the cells.

However, the introduction of such microcapsules in the body brings aboutsome problems, among which the following should be emphasized:

1) the microcapsules introduced in the body are wrapped in a reactiveconnective tissue, which prevents both the metabolic supply to the cellsand the leaking out of the secreted hormones;

2) the microcapsules, if injected into a cavity such as the peritonealcavity, tend to move downwards and concentrate in a limited area, thuscausing a lively connective reaction involving them.

SUMMARY OF THE INVENTION

The problems of the prior technique can be solved through the use of avascular prosthesis of a low porosity material, such as PTFE inside ofwhich is another prosthesis of a synthetic tubular mesh which allows foroxygen and hormones to pass through microcapsules of semi-permeablematerials, such as; polysaccharides and amino-acid polymers or, thatcontain the hormone-producing cells, are placed between the twoprostheses. The preparation of the vascular prosthesis involves thefollowing steps:

a) Inside of a vascular prosthesis of a low posity mesh such as PTFE asecond prosthesis is placed, made of a synthetic tubular mesh withexternal support (EXS);

b) the microcapsules which consist of, for example saccharide oramino-acid polymers and contain the hormone-producing cells are placedin the space between the two prosthesis and;

c) a spindle of a plastic material is then introduced into the interiorof the prosthesis.

Prostheses according to the present invention are used to createartervenous fistulas.

DETAILED DESCRIPTION OF THE INVENTION

The characteristics and advantages of the vascular prostheses and therelative preparation process, according to the present invention, willbe dealt with in greater detail in the following description, alsoreferring to the enclosed FIG. 1.

FIG. 1 represents schematically the prosthesis according to the presentinvention. With reference to the symbols of said figure, microcapsules2, containing the hormone-producing cells, are placed between aprosthesis 1 of PTFE or of a low porosity material and a prosthesis 3 ofa synthetic tubular mesh, and in said prosthesis 3 a plastic materialspindle 4 is introduced.

The tubular mesh is preferably made of polyester orpolytetrafluoroethylene fibers (for example, Dacron or Teflon fibers)and has an internal diameter of between 4 and 14 mm with an externalsupport (EXS).

The empty spaces between the filaments making up such mesh are between10 and 300 micron such that is such the microcapsules are retained.

The microcapsules are made of saccharide and amino-acid polymers orother semi-permeable material with a porosity of about 60.000 Dalton.This allows for the transfer of the metabolic products from the insideto the outside and viceversa, but not the passage of the immunoglobulinsor other high molecular weight molecules.

The spindle is preferably made of silastic or PVC and has an externaldiameter compatible with the internal diameter of prosthesis 3. Thespindle transforms the space between prosthesis 1 and prosthesis 3, inwhich the microcapsules 2 will be placed, into a virtual space. Theprosthesis according to the present invention is implanted, afterextraction of the spindle into the recipient through an artero-venousfistula.

A vascular prosthesis is thus obtained; consisting inside of a synthetictubular mesh that retains the microcapsules, which are in practiceexposed to the hematic flow and which is covered by an endothelium-liketissue.

In such vascular prosthesis the hematic flow allows for the metabolismof the cells contained in the microcapsules to exist and at the sametime it also allows for the circulation of the hormones secreted by thecells themselves.

A particularly useful application is possible when the microcapsulescontain Langherans islands cells which secrete insulin.

We claim:
 1. A process for the preparation of a vascular prosthesiscomprising:forming an outer material having a low porosity and an innertubular porous mesh of synthetic material said porous mesh having aporosity to allow oxygen and hormones to pass therethrough; disposingmicrocapsules between said outer material and said inner tubular mesh,said microcapsules being made of a semi-permeable material andcontaining hormone-producing cells; and introducing into said prosthesisa spindle of plastic material sized to be introduced into saidprosthesis.
 2. Process according to claim 1, wherein said spindle ismade of a material selected from the group consisting of silastic andPVC and has an external diameter compatible with the internal diameterof said mesh.
 3. Process according to claim 1, wherein said mesh is madeup of fibers selected from the group consisting of polyester andpolytetrafluoroethylene fibers.
 4. Process according to claim 1, whereinsaid tubular mesh has an internal diameter of between 4 and 14 mm. 5.Process according to claim 1, wherein free spaces between filamentsmaking up said mesh are of between 10 and 300 microns.